Is it possible to illuminate a planet artificially from orbit?

cosmictotem

cosmictotem

Registered Senior Member
Say if you had thousands of sats that were charged during the day by solar power and fitted with lights aimed at Earth,... would they always be too close and/or too weak to artificially illuminate large, dark sided sections of the planet with current technology?

And if that wouldn't work, what would you say ---no matter how improbable--- would be the technique and employment of technology that would come the closest to pulling it off?

Thanks.
 
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cosmictotem said:
Interesting. My concern with using actual sunlight reflected off mirrors instead of artificial light, is sunlight, if delivered in copious amount, might heat up the planet more than usual.
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Why do you think artificial light will not heat up the planet?

You can always tweak the mirrors to reflect only the frequencies of light you want. But either method is still going to heat up the Earth.
 
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cosmictotem said:
Don't we have artificial light that radiates light but not heat?
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Some LED bulb can radiate light well but not 100%. Light(Artificial/Natural) contains energy.The surface of a planet doesn't reflect 100% of incident light energy. Some of the light energy is absorbed by surface of a planet and the energy(absorbed) will transform into heat and other energy.
 
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ajanta said:
Some LED bulb can radiate light close to 100%. Light(Artificial/Natural) contains energy.The surface of a planet doesn't reflect 100% of incident light energy. Some of the light energy is absorbed by surface of a planet and the energy(absorbed) will transform into heat and other energy.
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So is there a difference between sunlight and LED rays? Does sunlight (rays) have to be absorbed by something or aren't they already hot before they reach Earth?

And do LED light rays leave the bulb hot?

Which brings up a good question: Is the existence of heat dependent upon an absorber?

I guess it is since something needs to get hot for temperature to exist.
 
reflected sunlight:
Several weather phenomena, such as precipitation and thunderstorm frequency, have been linked to the phase of the moon. Now, it seems that the moon's "cold" emanations can also raise the earth's temperature. Explaining how the moon's phase can have any warming effect at all on the earth's atmosphere is difficult, because the infrared energy received from the moon is only 10-5 that in sunlight. Nevertheless, a slight but statistically significant temperature effect does exist.

In one study, the microwave emission of molecular oxygen was measured by a polar-orbit satellite. These data gave meteorologists the temperatures of the lowest 6 kilometers of the atmosphere from all areas of the planet. The temperature difference between full moon and new moon was only 0.02°C, with the full-moon temperature being the higher. (Ref. 1)

A second study took actual surface temperatures measured at noon GMT each day at 51,200 locations around the world. These near-surface temperatures revealed a difference of 0.2°C between full and new moons --
... more...
http://www.science-frontiers.com/sf100/sf100g11.htm

more reflected sunlight:
Full moons at autumn were called harvest moons, and hunter's moons...
 
cosmictotem said:
So is there a difference between sunlight and LED rays?
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Yes. There are many kind of LED rays. But if it is possible to produce same LED ray of wavelength that Sun radiates so no difference between them.
cosmictotem said:
Does sunlight (rays) have to be absorbed by something or aren't they already hot before they reach Earth?

And do LED light rays leave the bulb hot?

.
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Actually light is made of photons. Photon carries energy and it is difficult to say that its already hot or not when photon carries energy. It has to transform energy to particles into heat that we feel(heat).

LED bulb transforms some light energy from its input electrical energy and transforms some heat energy from it(input electrical energy) also.
 
cosmictotem said:
Say if you had thousands of sats that were charged during the day by solar power and fitted with lights aimed at Earth,... would they always be too close and/or too weak to artificially illuminate large, dark sided sections of the planet with current technology? And if that wouldn't work, what would you say ---no matter how improbable--- would be the technique and employment of technology that would come the closest to pulling it off?
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There were "cheap" balloon satellites (like Echo 1, 2) that NASA started launching into orbit in 1960, which were only passive reflectors of communication signals. Like the aborted potential of Vladimir Syromyatniko's unfolded paper-thin disks, some nifty alternative designs to the original spherical balloons, with crafty angles for reflecting sunlight to a celestial body below, are probably possible. It's long-since been demonstrated that balloons can endure average space debris at that speed for at least a few years.

Of course, as with Syromyatniko's "mirror" project, there would be plenty of complaints (especially from astronomers) if they were deployed for Earth use.

http://motherboard.vice.com/read/the-man-who-turned-night-into-day
 
cosmictotem said:
So is there a difference between sunlight and LED rays? Does sunlight (rays) have to be absorbed by something or aren't they already hot before they reach Earth? And do LED light rays leave the bulb hot?
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No light is "hot." It is just light. It is only converted to heat when it strikes an object.

All frequencies "heat things up." 1000 watts per square meter of blue light hitting a black surface will heat it up as much as 1000 watts per square meter of infrared light hitting a black surface. It's just that we can't see infrared so it's not useful as light.
 
I think the bigger issue than technology/technique is motivation. Why would we want to do this?

Sure, the obvious reasons are longer growing season for crops, but in this day and age of global warming, do we really want to add more heat to the Earth?
 
Just to add to what already has been said, light in the visible range only will still cause surface heating. So the question is, how much night-time lighting would you want, and how much of an effect would it have? A full moon on a clear night illuminates the ground with ~1 lux. Standard office lighting runs from 320-500 lux. So if you want the "night" side to be illuminated as brightly as the interior of an office, then we are talking about 320 to 500 times as much light and that much more heating effect than the above mentioned amount for a full moon. ( actually it would be more, if we assume an equal amount of artificial lighting over the whole surface of the night side, as the present surface heating/lighting for the Moon falls off for regions not directly under the Moon.)
 
DaveC426913 said:
I think the bigger issue than technology/technique is motivation. Why would we want to do this?
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To reduce the need for lighting at night. Think of how much less CO2 we would generate if we didn't need lighting. Between 10 and 20% of all our energy generation goes to lighting.
Sure, the obvious reasons are longer growing season for crops, but in this day and age of global warming, do we really want to add more heat to the Earth?
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Well, keep in mind that if a big orbiting mirror is going to direct sun towards the earth at night, it can direct sun away from the earth when it is over the day side.
 
DaveC426913 said:
I think the bigger issue than technology/technique is motivation. Why would we want to do this?
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Solar energy collection efficiency. If possible, solar panels and Earth-based batteries then could collect and store energy from space 24/7.
 
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